SLC16A2 and hyperinsulinemic hypoglycemia, familial, 4: In a study of twenty-seven male patients with genetically confirmed MCT8 deficiency [mean age at evaluation: 9.3 years (range 0.9–18.5)], hypokinesia, often associated with hypomimia and global hypotonia, was present in twenty-five patients and was the predominant movement disorder in nineteen of those patients (18).